I have had this issue just recently and have tried everything possible to fix it. I've come to the conclusion there is no way to fix the problem, TinyUmbrella doesn't work, you will just get more errors with that program. IRev doesn't work, same thing more errors. None of the videos on YouTube have the answer (most are for Windows users). The only solution is to take it to a tech shop and get them to restore it for you. It will cost $60-$100 bucks and then you have to restore your service provider which will cost you another pile of money etc etc etc. :( Not the answer you where looking for.